I. Field of the Invention
The present invention relates generally to industrial ventilation fans, especially those adapted for agricultural use. More particularly, my invention relates to a fan that utilizes tensionable guards coupling to the housing to form a rigid overall structure with an universal internal bracing system.
II. Description of the Prior Art
It has long been recognized in the fan arts that moving air may be conveniently used to ventilate an area while simultaneously cooling it. Thus, directed high velocity air is often used for both ventilation and cooling purposes in many applications. For example, high velocity fans often provide ventilation and cooling for many agricultural facilities, especially in the poultry and dairy industries.
To practically control the effects of such fans, it is desirable to control the direction, velocity, and volume of the air being driven. I have previously proposed a fan adept at controlling air over long ranges. My previous invention, issued as U.S. Pat. No. 5,480,282, on Jan. 2, 1996, and its teachings are hereby incorporated by reference. It was classified in U.S. Class 415, subclass 125. As can be seen from that patent and the prior art therein, the known prior art comprises many different types and designs of fans adapted to satisfy various criteria.
Fans have been used for controlling temperature and removing gases in agricultural buildings, such as poultry confinement houses, since the middle of this century. During this time period, countless changes have been made in the fans to improve both their installation and their resultant ventilation and cooling effects. The consequence of these changes has been the development of a wide variety of fans. The fan housings and accessories have become especially diverse.
For example, a common exhaust fan installed in a conventionally mounted parallelepiped housing may be equipped with screen guards, shutters, discharge cones, as well as an extensive variety of drive arrangements and blades. The same exhaust fan may also be installed in a slanted orientation and then combined with other accessories to perform a different ventilation or cooling task altogether.
To further complicate matters, many manufacturers offer identical fans for both intake and exhaust applications while others build different intake and exhaust fans. Others build completely different fans for different applications. Furthermore, each time a new method of routing air or installing fans comes into vogue, many fan manufacturers simply change their designs to conform to the latest style. The result of such random change is many individual fans with specialized components and accessories that have very little interchangeability.
As may well be imagined, such diversity among fans and components causes countless maintenance nightmares. For one, multiple parts must be kept "on hand" to properly service or repair fans. Moreover, the technician servicing the fan generally must possess knowledge of several different types and designs of fans. Yet another problem involves the protective safety guards installed on most fans.
Protective safety guards prevent objects from inadvertently contacting the fan blades during operation. Such guards typically comprise rectangular wire mesh screens installed on both sides of the fan housing. On most fans, the guards must be removed to service the fan. Then, the guards must be replaced tightly on the housing. Otherwise they get loose, eventually becoming deformed and ineffective. Deformed guards are also difficult to remove and install properly.
Furthermore, the more a fan is used, the "looser" the fan housing gets. Internal vibrations and/or rough handling eventually cause the housing to become deformed or warped. As a result, the guards simply do not "fit" the housing as tightly as they did when the fan was newer. Thus, provision must be made for tensioning the guards properly as the fans age to avoid premature deformation and breakdown. An ideal tensioning system must inherently reinforce the structural stability of the housing.
Another problem with known prior art belt-driven fans is the lack of a simple belt tensioning method. As the fans age, wear on the belts, motors and associated pulleys results in less belt tension and subsequently poorer fan performance. To maintain peak operating efficiency, belt tensioning must be performed more often for older fans. Tensioning of belt-driven fans generally requires the removal of at least one guard. Unfortunately, this type of routine maintenance requires considerable time and effort. Consequently, a desirable fan would automatically maintain traction on the belt to encourage peak operating efficiency.